Fire retardant material and method of making the same

ABSTRACT

This invention is directed to a light weight fire resistant material. The material is constructed of a plurality of oxidized polyacrylonitrile (OPAN) fibers. The fire resistant material having a weight in the range of less than about 9.0 oz/yd2, an Arc Thermal Performance Value of greater than about 8.0 and a Thermal Protection Performance of greater than about 13.0.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/868,809, filed Aug. 26, 2010, which claims priority to U.S.Provisional Application No. 61/237,085, filed Aug. 26, 2009, the entiredisclosures of which are hereby expressly incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to an abrasion and fire resistant material and/ora fire resistant fabric. More particularly, the present inventionrelates to a fire resistant fabric containing oxidized polyacrylonitrilethat can be made into various types of lightweight fabric structureswith increased density and fire resistance.

2. Description of the Related Art

There is a continuing need to improve protection against flame, heat andflash fire for pilots, firefighters, steelworkers, and the like. This isparticularly critical for personnel who are frequently at close quarterswhen heat, flame and flash hazards occur. The primary line of protectionis the fabric comprising the protective clothing worn by the individual.In addition to providing protection, it is important that this clothingalso feel comfortable in order to increase the likelihood it will beworn at all times that the individual would be at risk.

The current lightweight fire resistant materials known in the art havedeficiencies. For example, some known lightweight fire retardantmaterials can melt and cling to the skin during exposure to severe heator flame as those used, for example, in military uniforms such as theBDU (battle dress uniform) which is made of 50% cotton and 50% nylon.Other fabrics, such as Nomex®, are plastic-based products which providefire protection by combusting (oxidizing) in a low flame manner andleaving behind a brittle Char that has some heat protectioncapabilities. Although these products do not melt and stick, they willbreak apart under the slightest dress or movement, leaving the wearernaked to a flame. The yarn of previous lightweight fire resistantmaterials, including inherently fire resistant fibers, had to be spun ina thick fashion in order to have sufficient strength for weaving.Therefore, the only way to produce a lightweight fabric was to takethese thick yarns and weave them loosely, which severely decreased thedensity, strength and fire resistant ability of the material.

Inherently fire resistant fibers are well-known to those skilled in theart. These fibers, known as matrix fibers, are useful because of theirfire resistant qualities but, are not strong enough to form their ownfabrics, tend to have a non-uniform composition, are not susceptible ofbeing easily dyed, and, in general, are not alone suitable forproduction into piece goods from which finished products, like clothing,are formed. On the other hand, conventional natural and synthetic fibers(staple fibers) which are alone suitable for production into finishedpiece goods, are not inherently fire resistant.

Accordingly, there remains a need for a fire resistant material capableof having a desirable density (thread count), weight, and fireresistance.

SUMMARY OF THE INVENTION

The invention is directed to a lightweight fire resistant material. Thematerial is constructed of a plurality of oxidized polyacrylonitrile(OPAN) fibers. The fire resistant material includes a weight in therange of less than about 9.0 oz/yd2, an Arc Thermal Performance Value ofgreater than about 8.0 and a Thermal Protection Performance of greaterthan about 13.0.

In another embodiment of the present invention, a method of providingthe lightweight fire resistant material is provided. The fire resistantmaterial is constructed by providing a plurality of oxidizedpolyacrylonitrile fibers. Once the oxidized polyacrylonitrile fibers areprovided, the oxidized polyacrylonitrile fibers are woven togetherwherein the fire resistant material has a weight in the range of lessthan about 9.0 oz/yd2, an Arc Thermal Performance Value of greater thanabout 8.0 and a Thermal Protection Performance of greater than about13.0.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a fire resistant material. The fireresistant material can be a yarn, a fabric made from the yarn, felt, anytype of fibrous blend, and/or a combination thereof. In accordance withthe present invention, the fire resistant material includes oxidizedpolyacrylonitrile (OPAN) fibers to provide high fire and heat resistanceto the fire resistant material.

In addition to the OPAN, the fire resistant material can include othertypes of fibers to provide the fire resistant material with variouscharacteristics. For example, additional fibers can be included toimpart tensile strength, tear strength and abrasion resistance to thefire resistant material. The fibers of the fire resistant material canbe woven, knitted, or otherwise assembled into appropriate fabrics tomake a wide variety of fire and heat resistant articles of manufacturesuch as clothing, jump suits, gloves, socks, welding bibs, fireblankets, floor boards, padding, protective head gear, linings,undergarments, cargo holds, bedding, mattress insulation, drapes,insulating fire walls, and the like. It should be understood andappreciated that the OPAN fibers and the additional fibers can beblended in any manner known in the art for blending various differenttypes of fibers.

The OPAN fibers are included in the fire resistant material in anyamount such that the desired fire resistance is provided to the fireresistant material. The OPAN fibers can be included in the presentinvention in a range of from about 1% to 100% by weight of the fireresistant material. In one embodiment of the present invention, the OPANfibers are provided in a range of from about 25% to about 99.9% byweight of the fire resistant material. In another embodiment of thepresent invention, the OPAN fibers are provided in a range of from about25% to about 85% by weight of the fire resistant material. In a furtherembodiment of the present invention, the OPAN fibers are provided in arange of from about 30% to about 75% by weight of the fire resistantmaterial.

The OPAN fibers can be any length such that the desired fire resistanceis provided to the fire resistant material. Longer OPAN fibers providesthe fire resistant material with higher tensile strength. In oneembodiment of the present invention, the OPAN fibers can be provided inlengths in a range of from about 50 mm to about 100 mm. In anotherembodiment of the present invention, the OPAN fibers can be provided inlengths in a range of from about 70 mm to about 80 mm. In yet anotherembodiment of the present invention, the OPAN fibers can be provided inlengths in a range of from about 73 mm to about 76 mm.

In a further embodiment of the present invention, the OPAN fibers canhave any linear mass density or specific gravity such that the fireresistant material has the desired physical characteristics. In oneembodiment of the present invention, the linear mass density of the OPANfibers is in a range of from about 1.5 denier to about 3.0 denier. Inanother embodiment of the present invention, the linear mass density ofthe OPAN fibers is about 2.0 denier. In a further embodiment of thepresent invention, the specific gravity of the OPAN fibers is in a rangeof from about 1.2 to about 1.6. In yet another embodiment of the presentinvention, the specific gravity of the OPAN fibers is in a range of fromabout 1.35 to about 1.47.

Examples of additional fibers that can be provided in the fire resistantmaterial includes, but is not limited to, polyvinyl halide,polybenzimidazole (PBI), polyphenylene-2,6-benzobisoxazole (PBO)para-aramid, meta-aramid, modacrylic, wool, fire resistant wool, fireresistant nylon, cotton, melamine, fire resistant polyester, fireresistant rayon, and combinations thereof.

Para-aramid fiber can be added to the fire resistant material to addstrength to the fire resistant material. The para-aramid can be sized soas to provide optimal strength to the fire resistant material. In oneembodiment of the present invention, the fire resistant material can beprovided with para-aramid fibers having a length in a range of about 38mm to about 76 mm. In another embodiment of the present invention, thefire resistant material can be provided with para-aramid fibers having alength of about 50 mm.

The additional fibers can be added to the fire resistant material in anyamount such that desired characteristics associated with the specificadditional fibers are imparted on the fire resistant material to providethe fire resistant material with the desired physical properties. In oneembodiment, the additional fibers can be provided in an amount of lessthan about 75% by weight of the fire resistant material. In anotherembodiment of the present invention, the additional fibers can beprovided in an amount of from about 25% to about 65% by weight of thefire resistant material.

The fire resistant material of the present invention can be constructedsuch that the material has warp lines (or long lines in the material)and weft lines (or short lines in the material). In another embodimentof the present invention, the fire resistant material is provided withstainless steel fibers to retard the static buildup in the fireresistant material. In a further embodiment of the present invention,the stainless steel fibers are only provided in the weft lines of thefire resistant material.

The stainless steel fibers can be included in the fire resistantmaterials in any amount such that the desired static resistance ordesired static buildup retardance is achieved. In one embodiment of thepresent invention, the stainless steel fibers can be included in thefire resistant material in an amount in a range of less than about 2.0%.

In another embodiment of the present invention, the fire resistantmaterial is constructed of longer fibers. These longer fibers allow forthe creation of thinner yarns. The thinner yarns created from the longerfibers have a yarn count of Nm 1/48. The thinner and stronger yarn inthe fire resistant material provides the fire resistant material with athinner, stronger and more dense fabric while still maintaining alighter weight. Further, the fire resistant material constructed withlonger fibers has a higher thread count than fire resistant materialmade with a yarn count of Nm 1/36, for example. In another embodiment ofthe present invention, the thinner yarns have a yarn count of Nm 2/48.Similarly, the yarn count of Nm 2/48 has a higher thread count thanmaterial made with a yarn count of Nm 2/36.

The fire resistant material constructed in accordance with the presentinvention can be fabricated such that the material can have a specificweight. In one embodiment of the present invention, the fire resistantmaterial is provided with a weight in a range of less than about 9.0oz/yd2. In another embodiment of the present invention, the fireresistant material is provided with a weight in a range of less thanabout 7.0 oz/yd2. The fire resistant material of the present invention,while being less than about 7.0 oz/yd2, will have an Arc ThermalPerformance Value (ATPV) of greater than about 8.0 and a ThermalProtection Performance (TPP) value of greater than about 13.

In another embodiment of the present invention, chitosan can be appliedon/to the fire resistant material to greatly increase the fire resistantcapability of the fire resistant material. The amount of chitosan thatcan be used can be any amount such that the fire resistant material hasthe desired fire resistance. In one embodiment, the amount of chitosanused is in a range of from about 0.1% to about 10.0% by weight of thefire resistant material.

The chitosan can be bonded to the fire resistant material by mixing thechitosan in a solvent and then applying the resultant solution to thefire resistant material. Examples of solvents include, but are notlimited to, acetic acid and citric acid. It should be understood andappreciated that the solvent can by any material known in the art forbeing able to properly apply chitosan to the fire resistant material.

In a test conducted; by GSL, a non-chitosan treated fire resistantmaterial, about 8 oz/sq yard of fire resistant material was subjected toa propane torch rated at 1800° F.-2000° F. from a distance of about 12inches. After being continuously subjected to the flame for a period ofabout 7 minutes, a small hole was ablated through the fabric. As acomparison, the same test was run against an identical piece of fireresistant material, with the exception being a treatment of chitosan wasapplied to the fabric and allowed to dry before onset of the flame test.The result was an additional burn-through protection time of about 7minutes. This chitosan treatment doubled the already significant burnthrough protection of the fire resistant material.

Combined Heat and Stress Fabric Test

Recognizing the inadequacies of current certification tests, an enhancedfabric fire test was designed. This test adds a simulation of real worldelements by placing the tested fabric under stress. The stress isdesigned to simulate the same fabric pressures resulting from normalbodily movements, such as bending, twisting and stretching. The materialof the present invention outperforms other fabrics by an order ofmagnitude.

Such movements would normally be experienced, for example, when enteringor exiting a vehicle compartment or from downward pressure exerted byequipment attached to an individuals clothing (e.g. a soldier'suniform). Running from one location to the next would also place stresson the fabric. Fire resistant fabrics would probably experience moresevere stress when an injured individual is pulled from a burningvehicle, especially if the rescuer were to use the fabric as a handle topull a person to safety.

This test apparatus was modeled after ASTM D 6413, Flame Resistance ofTextiles (Vertical Test) (1999). This test incorporated a test stand tosupport a strip of fabric. The test apparatus consisted of a stationarystand with a top and bottom set of metal plates held together by a threewing nuts. The top plates were stationary, with the bottom plates havingthe ability to move freely in a vertical motion on the stand. One inchof fabric was inserted between the top two metal plates. When the fabricwas level the wing nuts were, tightened thereby securing the fabric fromslipping. The bottom plates were then brought up to meet the bottom ofthe fabric so that an inch of fabric could be inserted and secured.After the fabric was secured, a 6 in. by 11.5 in. fabric strip was leftfor burning/testing. The bottom plate exerted 3.15 pounds of force tothe fabric.

Next, a flame heat source was aligned to focus 2.2 cal/cm2-sec on thecenter of the fabric strip. Time was recorded from when the torch wasstarted until the fabric strip broke apart as a result of the heat andstress exerted on the test sample. The results for various fireretardant fabrics are shown in Table 1. It should be understood andappreciated that Spentex® is the commercial name of the fire resistantmaterial constructed in accordance with the present invention.

TABLE 1 Seconds before Heat/Stress Break Open. Average Time StressFabric Burned Pull Force Applied to Before Breaking Fabric Brand(pounds) Fabric (psi) (seconds) Nomex ® IIIA 3.15 32.8 0.65 Blended FRCotton 3.15 32.8 1.285 (88/12) 7 oz. Spentex ® 3.15 32.8 36.195

From the above description, it is clear that the present invention iswell adapted to carry out the objectives and to attain the advantagesmentioned herein as well as those inherent in the invention. Whilepresently preferred embodiments of the invention have been described forpurposes of this disclosure, it will be understood that numerous changesmay be made which will readily suggest themselves to those skilled inthe art and which are accomplished within the spirit of the inventiondisclosed and claimed.

What is claimed is:
 1. A lightweight fire resistant material, the material comprising: a plurality of oxidized polyacrylonitrile fibers wherein the fire resistant material has a weight in the range of less than about 9.0 oz/yd2, an Arc Thermal Performance Value of greater than about 8.0 and a Thermal Protection Performance of greater than about 13.0.
 2. The material of claim 1, wherein oxidized polyacrylonitrile fibers of the fire resistant material are provided in a length in a range of from about 73 mm to about 76 mm.
 3. The material of claim 1, wherein the weight of the fire resistant material is in a range of less than about 7.0 oz/yd2.
 4. The material of claim 1, wherein the specific gravity of the oxidized polyacrylonitrile fibers is in a range of from about 1.35 to about 1.47.
 5. The material of claim 1, wherein the linear mass density of the oxidized polyacrylonitrile fibers is in a range of from about 1.2 denier to about 3.0 denier.
 6. The material of claim 1, wherein the fire resistant material further includes para-aramid fibers.
 7. The material of claim 6, wherein the para-aramid fibers have a fiber length in a range of from about 38 mm to about 76 mm.
 8. The material of claim 1, wherein the oxidized polyacrylonitrile fibers are present in the fire resistant material in an amount of from about 1% by weight to about 100% by weight.
 9. The material of claim 1, wherein the oxidized polyacrylonitrile fibers are present in the fire resistant material in an amount of from about 30% by weight to about 70% by weight.
 10. A method of providing a lightweight fire resistant material, the method comprising the steps of: providing a plurality of oxidized polyacrylonitrile fibers; and weaving the plurality of oxidized polyacrylonitrile fibers together wherein the fire resistant material has a weight in the range of less than about 9.0 oz/yd2, an Arc Thermal Performance Value of greater than about 8.0 and a Thermal Protection Performance of greater than about 13.0.
 11. The method of claim 10, wherein oxidized polyacrylonitrile fibers of the fire resistant material are provided in a length in a range of from about 73 mm to about 76 mm.
 12. The method of claim 10, wherein the weight of the fire resistant material is in a range of less than about 7.0 oz/yd2.
 13. The method of claim 10, wherein the specific gravity of the oxidized polyacrylonitrile fibers is in a range of from about 1.35 to about 1.47.
 14. The method of claim 10, wherein the linear mass density of the oxidized polyacrylonitrile fibers is in a range of from about 1.2 denier to about 3.0 denier.
 15. The method of claim 10, wherein the fire resistant material further includes para-aramid fibers.
 16. The method of claim 15, wherein the para-aramid fibers have a fiber length of from about 38 mm to about 76 mm.
 17. The method of claim 10, wherein the oxidized polyacrylonitrile fibers are present in the fire resistant material in an amount of from about 1% by weight to about 100% by weight.
 18. The method of claim 10, wherein the oxidized polyacrylonitrile fibers are present in the fire resistant material in an amount of from about 30% by weight to about 70% by weight.
 19. A fire resistant material, the material comprising: a plurality of oxidized polyacrylonitrile fibers; and an amount of chitosan applied to the plurality of oxidized polyacrylonitrile fibers to increase the fire resistance of the fire resistant material.
 20. The material of claim 19, where in the amount of chitosan applied is in a range of from about 0.1% to about 10.0% by weight of the fire resistant material.
 21. A method of providing a fire resistant material, the method comprising the steps of: providing a plurality of oxidized polyacrylonitrile fibers; applying an amount of chitosan to the plurality of oxidized polyacrylonitrile fibers to increase the fire resistance of the fire resistant material; and weaving the plurality of oxidized polyacrylonitrile fibers together.
 22. The method of claim 21, wherein the chitosan is applied in an amount in the range of from about 0.1% to about 10.0% by weight of the fire resistant material. 